An approximate Hartree-Fock self-consistent-field (SCF) calculation has been carried out for the (NiF6)4- cluster. Exponential-type orbitals with four independent radial functions were employed for the nickel 3d electrons, two radial functions for the fluorine 1s and 2s electrons, and one for the fluorine 2p electrons. A core potential was used to represent the metal (1s-3p) electrons. All one-electron integrals and all one- and two-center two-electron integrals were evaluated. A closed-shell SCF program was used with orbital occupation numbers adjusted to approximate the open shell. The results of comparisons at different stages in the convergence of the SCF iteration show large differences in 10Dq and the degree of delocalization. This implies that some of the earlier simplifications of the SCF treatment are not valid; that is, significant ligand (2s-2pσ) mixing is found and the metal 3d functions make an important contribution to the bonding orbitals. © 1971 The American Physical Society.